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One possible source of the rubbing which has not as yet been mentioned would be a gear block spacer.
This is a plain washer fitted between the hub shell and the gear block in order to fine tune the chainline.
The common thickness is 1.5mm, however 1.0mm and 2.0mm were also used.
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The Schwinn Approved gear blocks which came in ca. 1973-74 with the large splined opening for a remover are Normandy brand as manufactured in France by the firm of Maillard.
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